Thin film transistor-liquid crystal displays (TFT-LCD) have features such as small size, low power consumption, no radiation, etc., have developed rapidly in recent years and dominated the current flat display device market. A liquid crystal panel is a core component of a TFT-LECD, and includes an array substrate and a color filter substrate that are oppositely arranged to form a cell, as well as liquid crystal filled between the array substrate and the color filter substrate. Currently, a liquid crystal dropping process, that is, one drop fill (ODF) process has been adopted in a cell manufacturing process of the liquid crystal panel. The ODF process specifically includes: first coating liquid crystal and sealant on a surface of the array substrate or the color filter substrate, and then performing a cell alignment process. This requires the sealant around the liquid crystal panel to be cured in the shortest time, so that the liquid crystal is prevented from being polluted by uncured sealant so as not to affect product quality.
The existing sealant curing includes UV curing and thermal curing. In a sealant UV curing device, a mask plate is fixed by a vacuum adsorption device between a UV light source and a liquid crystal panel with sealant to be pre-cured. Specifically, the mask plate may be fixed by a plurality of quartz rods with grooves through vacuum adsorption, and the liquid crystal panel is fixed on a bearing platform. The UV light source is composed of a plurality of UV light tubes which are uniformly distributed above the mask plate and emit downwardly UV light. The mask plate includes a light transmission region and a light shielding region. The UV light passes through the light transmission region to cure the sealant. The light shielding region covers a display region of the liquid crystal panel to protect the display region from being irradiated by the UV light. After completion of the UV curing, the liquid crystal panel is transferred to a thermal curing device, for example, a baking oven, so as to thermally curing the sealant under conditions of greater than 100° C. Finally, after completion of the curing, the liquid crystal panel is cooled.
In production process, the liquid crystal panel with the sealant to be pre-cured is raised by the bearing platform from a delivery position which is far relative to the mask plate (at the delivery position, a distance between the mask plate and the liquid crystal panel is much greater than 3 mm) to an exposure position (where a distance between the mask plate and the liquid crystal panel is about 3 mm), and then exposure is started to cure the sealant. After the completion of the exposure, the liquid crystal panel is moved downwardly from the exposure position to the delivery position. At the beginning of the downward movement, since the distance between the mask plate and the liquid crystal panel is too small, with an increasing distance between the mask plate and the liquid crystal panel, air pressure between the mask plate and the liquid crystal panel is smaller than that of ambient air, i.e., forming a pressure difference. Under action of the pressure difference, ambient air enters into space between the mask plate and the liquid crystal panel through gaps between the mask plate and the liquid crystal panel, and fills the space between the mask plate and the liquid crystal panel. Since the liquid crystal panel is on the bearing platform and is adsorbed by the bearing platform through vacuum adsorption, thus, there is no pressure on one side of the liquid crystal panel. Then, a pressure force generated by the above pressure difference is applied to the mask plate by air above the mask plate, this adversely increases load of the vacuum grooves of the quartz rods for adsorbing the mask plate. When the load exceeds the adsorption capacity of the vacuum grooves of the quartz rods, the mask plate falls from the quartz rods, and sticks to the liquid crystal panel which is located below the mask plate, resulting in damage of the liquid crystal panel.
Currently, in production process, after the completion of the exposure, the movement speed of the liquid crystal panel is reduced to alleviate the above technical problem, but this has seriously affected product yield, and it is difficult to achieve desired effects.